Thermosetting coating composition containing a blocked acid as catalyst

Abstract

A thermosetting coating composition containing an acid-curable amino resin and from 0,1 to 10 percent by weight of a blocked sulphonic acid, calculated on the weight of amino resin. The blocked acid used is an O-sulphonyl hydroxamic ester of the formula [RSO2ONHCOO]nA, wherein n represents an integer from 1 to 5 and R and A are organic groups. The new blocked acids are better soluble in the current solvents used in these coating compositions. The compositions may be used advantageously for coating a substrate by electrostatic spraying.

I claim: 
     
       1. A thermosetting coating composition containing an acid curable amino resin and an amount of a blocked acid corresponding to 0,1 to 10 percent by weight, calculated on the amino resin of potentially available sulphonic acid, characterized in that the blocked acid is an O-sulphonyl hydroxamic ester of the formula: [RSO 2  ONHCOO] n  A, wherein n represents an integer from 1 to 5 and A, when n=1, has the meaning of a substituted or unsubstituted alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl or heterocyclic group or when n=2 to 5 has the meaning of substituted or unsubstituted alkylene, cycloalkylene, arylene or alkarylene group and R represents a substituted or unsubstituted alkyl, alkenyl, cycloalkyl, aryl or heterocyclic group. 
     
     
       2. The coating composition of claim 1, wherein A represents a group having not more than 20 carbon atoms and R a group having not more than 35 carbon atoms. 
     
     
       3. The coating composition of claim 1 or 2, wherein n=1, and A represents an alkyl group or aralkyl group having not more than 10 carbon atoms and R a lower alkyl group or a phenyl group substituted or not with an alkyl group having not more than 20 carbon atoms. 
     
     
       4. The coating composition of claim 1 or 2, wherein n=2, and A is (CH 2 ) m  with m=2 to 10. 
     
     
       5. The coating composition of claim 3, wherein the blocked acid is O-methanesulphonyl ethoxyhydroxamate or O-p-toluenesulphonyl ethoxyhydroxamate. 
     
     
       6. The coating composition of claim 3, wherein the blocked acid is O-methanesulphonyl benzyloxyhydroxamate or O-p-toluenesulphonyl benzyloxyhydroxamate. 
     
     
       7. The coating composition of claim 1, wherein the blocked acid is ethylene dioxy bis(O-methane sulphonyl hydroxamate) or ethylene dioxy bis(O-p-toluene sulphonyl hydroxamate). 
     
     
       8. The coating composition of claim 1, 2, 3, 4, 5, 6 or 7, which also contains an amine. 
     
     
       9. The coating composition of claim 8, wherein the weight ratio between the blocked acid and the amine is between 0,02 and 0,15% by weight, calculated on the coating composition. 
     
     
       10. As a new article of manufacture, an article coated with the coating composition of claim 1.